The coating compositions of interest in the present invention are alkyd coating compositions, Type I urethane coating compositions, and unsaturated polyester resin coating compositions, typically a paint, clear coating, or stain. All the above-listed coating compositions after drying or curing show low hexadecane contact angles, are readily wetted by oil, and are susceptible to soiling. The coating compositions are described in Outlines of Paint Technology, Halstead Press, New York N.Y., Third edition, 1990) and Surface Coatings Vol. I, Raw Materials and Their Usage (Chapman and Hall, New York N.Y., Second Edition, 1984). A common factor in these coating compositions is an unsaturated resin or prepolymer structure that permits the polymerization of olefinic groups in the backbone or sidechain.
Conventional alkyd coatings utilize, as the binder or film-forming component, a curing or drying alkyd resin. Alkyd resin coating compositions contain unsaturated aliphatic acid residues derived from the drying oils. These resins spontaneously polymerize in the presence of oxygen or air to yield a solid protective film. The polymerization is termed "drying" or "curing" and occurs as a result of autoxidation of the unsaturated carbon-carbon bonds in the aliphatic acid component of the oil by atmospheric oxygen. When applied to a surface as a thin liquid layer of formulated alkyd coating, the cured films that form are relatively hard, non-melting, and substantially insoluble in many organic solvents that act as solvents or thinners for the unoxidized alkyd resin or drying oil. Such drying oils have been used as raw materials for oil-based coatings and are described in the literature.
Urethane coatings are classified by ASTM D-1 into five categories. Type I urethane coatings contain a pre-reacted autoxidizable binder as described in Surface Coatings Vol. I, previously cited. Type I urethane binders, also termed urethane oils, oil-modified polyurethanes, or urethane alkyds, are the largest volume category of polyurethane coatings, and include typical paints, clear coatings, or stains. Urethane coatings typically contain the reaction product of a polyisocyanate, usually toluene diisocyanate, and a polyhydric alcohol ester of drying oil acids. The cured coating is formed by air oxidation and polymerization of the unsaturated drying oil residue in the binder.
Unsaturated polyester resins contain as the unsaturated prepolymer the product obtained from the condensation polymerization of a glycol such as 1,2-propylene glycol or 1,3-butylene glycol with an unsaturated acid such as maleic (or of maleic and a saturated acid, e.g., phthalic) in the form of anhydrides. The unsaturated prepolymer is a linear polymer containing unsaturation in the chain. This is dissolved in a suitable monomer, for instance styrene, to produce the final resin. The film is produced by copolymerization of the linear polymer and monomer by means of a free radical mechanism. The free radicals can be generated by heat, or more usually by addition of a peroxide, such as benzoyl peroxide, separately packaged and added before use. Such coating compositions are frequently termed "gel coat" finishes. In order that curing can take place at room temperature the decomposition of peroxides into free radicals is catalyzed by certain metal ions, usually cobalt. The solutions of peroxide and cobalt compound are added separately to the mix and well stirred before application. The unsaturated polyester resins that cure by a free radical mechanism are also suited to irradiation curing, using, for instance, ultraviolet light. This form of cure, in which no heat is produced, is particularly suited to films on wood or board. Other radiation sources, for instance electron-beam curing, are also used.
Certain fluorinated materials are known to provide oil repellency to substrates such as textiles and carpets. For instance, perfluoroalkyl iodides have been converted sequentially to perfluoroalkyl ethyl iodides, to perfluoroalkyl ethyl alcohols, to monomers and finally polymers for application to such substrates.
The use of fluoroalkyl alcohol esters of alkanoic acids generally as lubricating aids is known. For instance, the perfluoroalkyl ethyl ester of stearic acid (octadecanoic acid) has been used for imparting lubricity and repellency to various plastics. Also, Nishihara et al., JP308469 (1989) disclose the preparation of aliphatic carboxylic acid esters of various fluorinated alcohols in general as lubricants and their use as lubricants for ferromagnetic metal thin film-type magnetic recording media.
Adding perfluoroalkyl ethyl stearate, a noncuring ("non-drying") fluoroalkyl ethanol ester of a saturated vegetable oil, for instance, to alkyd, urethane, or unsaturated polyester coatings in suitable formulations, however, does not provide durable oil and water repellency. Since the fluorinated component is saturated, it is not chemically bound with the cured polymer. Thus the oil repellency is not durable and is readily lost when the surface is washed or otherwise cleaned. By durable oil repellency and durable increased hexadecane contact angles are meant that the surface properties of the cured coatings are retained following surface cleaning.
Certain perfluoroalkyl ethyl esters that do not react with enamel binders have been listed by Deibig et al. in German patent DE 28 21 495 C2 and include bis(perfluorohexylethyl) maleate. Bis(perfluoroalkylethyl) maleate esters behave similarly to the stearyl esters and do not show durable oil repellency after scrubbing. Presumably the double bond in the ester is sufficiently deactivated by two immediately adjacent fluoroalcohol ester groups and is not sufficiently incorporated into the binder to provide durable oil repellency.
It is highly desirable to be able to provide cost effective and wash resistant oil repellency to alkyd coatings, Type I urethane coatings, and unsaturated polyester coatings. The present invention provides such compositions.